When Jesse visits Ethan's sister and her family for the first time her son can be clearly seen mouthing his sister's lines at the same time.
During the middle of the film when Ethan is with Jessi at her apartment; right before Troy comes over. You see the plant behind her that Ethan had gotten her since she claimed to not own any. When the camera goes back to Ethan, you can clearly see another plant behind him.
When Ethan and Jess are leaving his sister's house, Ethan unlocks and opens the car door for Jess. However, it is clearly visible that the door was already unlocked.